Cowled dome liner for combustors



March 29, 1960 E. v. JARAMILLO 2,930,193

COWLED DOME LINER FOR COMBUSTORS Filed Aug. 29, 1955 INVENTOR. [0/7480 kJIPWl/Zlfl United ee COWLED DOME LINER FOR COMBUSTORS Edward Vernon Jaramillo, Des Moines, Iowa, assignor gr; General Electric Company, a corporation of New ork Application August 29, 1955, Serial No. 530,936 6 Claims. (Cl. 60- -39.65)

The present invention relates to a, combustion apparatus and more particularly to an improved liner for combustion chambers.

Heretofore, the cowled dome liners used in cannular or annular type combustion systems have had a cowl of substantially the same diameter as the secondary zone. This necessitated placing the dome inside the liner and required the use of a transition section between the dome and the secondary or mixing region. This construction has imposed limits on the degree to which the liner can be scaled down to save weight and space without impairing the ignition and blowout characteristics of the liner. This problem comes about from the fact that when the dome and primary zone diameters are decreased to a certain point the quenching effects tend to become predominant because the metal walls of the dome actually conduct so much heat away from the combustion zone as to prevent adequate burning. Furthermore, the use of the transition section between the combustion zone and the secondary region presents a cooling problem due to the vortex created at this point which acts as a flameholder and subjects the transition section to constant flame.

The present invention provides a means of improving the blowout limits and ignition characteristics of cowled dome liners and of obtaining increased uniformity of temperature distribution of the products of combustion.

These results are obtained by the provision of a liner having an enlarged dome of increased diameter and a tapered mixing section. The cowl is placed on the outside of the dome in close proximity to the walls of the combustion chamber. The dome is attached directly to the mixing section thus doing away wtih the necessity of the transition section.

An object of the present invention is the provision of a' combustion chamber liner for obtaining improved uniformity of temperature distribution of the products of combustion at the exit end of the liner.

Another object is to increase the combustion efiiciency of combustion apparatus by increasing the residence time in the primary combustion zone.

An additional object is the provision of an improved liner arrangement which permits a major reduction in the overall length of the combustion system.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. 1 is an elevation view in longitudinal section showing'one' embodiment of an enlarged dome, tapered mixing section, cowled dome liner according to the present invention; and V Fig. 2 is a view similar to Fig. 1 showing a further embodiment of the present invention.

Referring more particularly to Fig. 1 of the drawing, the cowled dome liner of the present invention consists pf a dome 11 which defines the primary combustion zone,

a tapered mixing section 12 which is connected directly to the dome 11, and an enlarged cowl 13 which is positioned on the outside of the dome. The dome is provided with three spaced bands of openings 14, 15, and- 16 and a plurality of louvres 17 positioned at intervals over the entire surface of the dome. A fuel nozzle 18 shown in broken line, is positioned in the opening 19 at the apex of the dome. The wall of the mixing section 12 is convergent over a portion of its length and -is provided with seven bands of openings 21 through 27 and the louvres 28. The cowl-13 surrounds the dome andis spaced therefrom with the trailing edges of the cowl converging toward -the trailing edges of the dome. The leading edge of the mixing section is attached to the trailing edges of the cowl and the trailing edges of the dome as at 29 by rivets or other suitable heat resistant connec' tions. The trailing edge of the mixing section is attached to a conduit 31 which conducts the products ofcombus tion to a suitable consumer (not shown). The leading edge or snout 32 of the cowl extends upstream into the diffuser section 33 of the combustion chamber 34.

In the operation of the present invention, the snout 32 receives primary air in the diffuser section 33 upstream of the poor velocity profile which develops due to uneven diifusion. This primary air is conducted into the space between the cowl and the domewhich forms a plenum chamber assuring uniform positive static pressure over the entire surface of the dome. Part 'of the primary air is then injected through the openings 14, 15, and 16 in jets, creating turbulence within the primary combustion zone and assuring adequate burning of the fuel. The remaining primary air is forced through the louvres 17 and forms a film of cooling air over the entire inner surface of the dome. The enlarged dome of the present liner serves a twofold purpose, i.e., t o improve the blowout limits and to increase the combustion efiiciency. Since the walls of the dome are spaced farther apart, the quenching effect is reduced and the blowout limits are improved. In addition, dueto the enlarged space within the dome the primary combustion zone velocity is decreased, thereby increasing the residence time in the primary zoneand increasing the combustion efiiciency. The products of combustion flow from the primary combustion zone into the convergent mixing section where due to the diminished cross-sectional area the velocity of flow is increased and the static pressure is correspondingly decreased. The secondary air flows around the outside of the cowl and its velocity is accelerated as it passses through the restricted openings between the cowl and the walls of the chamber. This area is immune to Bernoulli effects, thus permittingf higher reference velocities than have previously been pose sible. Since the trailing edge of the cowl and the leading edge of the mixing section are tapered away fromthe.

walls of the chamber 34 the secondary air is difiused-in this space resulting in a decreased velocity and increased static pressure. This difiusion can be used to serve the same purpose as a diffuser in front of the combustor; therefore, a shorter ditfuseris possible. The secondary air is then injected in jets through the openings21 to27 into the mixing section where it quenches the combustion gases and materially reduces the temperature thereof. In addition, a portion of the remaining secondary air is forced through the louvres 28 where it forms a film of cooling air over the interior of the mixing section- Due to the taper of the cowl and of the mixing section, the static pressure of the gases within the mixing section is decreased and that of the secondary air surrounding the mixing section is increased. Thus, the pressure differential across the openings. 21 through 27 is increased permitting a deeper penetration of the jets of .secondaryair into the mixing section with consequentmore complete 2,930,193 Patented M 29 mixing .which in turn results in a moreuniform temperature distribution of the products of combustion.

The cowl dome liner of Fig. 2 is similar to that of Fig. 1 except .that the mixing section 35 converges throughout its length and is attached directly to the consumer at its trailing edge, thus eliminating the necessity of a conduit therebetween. This cowled dome liner may be used in a cannular type system, but it is of particular advantage in an annular combustion system wherein an annular liner is inserted within an annular combustion chamber. In this modification the mixing section 35 is taperedconvergently throughout its length, and as a result of this taper the jets of secondary air injected through the bands of openings are closer together. The leading edge of the cowl 38 extends upstream into the diffuser section 36, but due to the annular construction of this typesystem it can be designed so that little diffusion of secondary air takes place in the diffuser. Instead, the secondary air is diffused in the space 37 between the walls of the chamber 39 and the tapered cowl and mixing section, thereby facilitating the use of a much shorter diffuser. The increased pressure. differential. across the bands of openings, resulting from the increased taper of the mixing section andthegreater diffusion in the space 37, combined with the closer proximity of the jets of air produces a greater degree of mixing in the mixing section and results in a higher uniformity of temperature distribution of the products of combustion. This modification is additionally advantageous in that the conduit between the liner itself and the consumer is dispensed with and the trailing edges of the liner itself are connected to the consumer. The overall length of the combustion system is thereby materially reduced due to the shortened diffuser and the elimination of the conduit.

While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention and it isintended to cover in the appended claims all such changes and modifications that come within the true spirit and scope of the invention.

What is claimed is:

1. A cowled dome liner for combustion systems comprising, a dome section defining the primary combustion zone; an enlarged cowl spaced from and surrounding the dome with the trailing edges of the cowl converging toward the dome, the leading edges of the cowl forming a primary air intake, the space between the cowl and the dome forming a plenum chamber for the equalization of primary air pressure over the entire surface of the dome; a mixing section connected directly to the trailing edges of the dome and the cowl, the walls of said mixing section converging over at least a portion of their length and being provided with a plurality of openings therein; thereby increasing the pressure difierential between the inside and the outside of the mixing section permitting more uniform quenching of the combustion gases.

2. For use in a combustion system including a combustion chamber and a diffuser supplying primary and secondary air, a cowled dome liner adapted to be positioned in said chamber, said liner comprising: a dome section defining the. primary combustion zone; an enlarged cowl spaced from and surrounding the dome, the trailing edges of the cowl converging toward the dome, said cowl having a protruding snout adapted to extend upstream of the dome into the diffuser, to receive primary air having a good velocity profile, the space between the cowl and the dome. forming a plenum chamber for the equalization of primary air pressure over the entire surface of the dome; a mixing section connected directly to the trailing edges of the dome and the cowl, the walls of said mixing section converging over at least a portionof their length; thereby permitting the difiusion of secondary be ween. the Wa ls f the. nni st pq .shembsl an the convergent portions of the cowl and the mixing section.

3. A cowled dome liner for combustion systems comprising: a dome section defining the primary combustion zone; an enlarged cowl spaced from and surrounding the dome, the trailing edges of the cowl converging toward and secured to the dome, the space between the cowl and the dome forming a plenum chamber for the equalization of primary air pressure over the entire surface of the dome; a mixing section connected directly to the dome, the walls of said mixing section converging over their entire length and having a plurality of openings therein; thereby providing means for increasing the static pressure differential between the inside of the mixing section and the outside thereof and permitting uniform quenching of the combustion gases.

4. For use in combustion system including an annular combustion chamber and an annular diffuser supplying primary and secondary air, an annular cowled dome liner adapted to be positioned in said chamber, said liner coniprising; a dome section defining the primary combustion zone, said dome having a plurality of openings therein; a cowl spaced from and surrounding the dome, the trailing edges of the cowl converging toward the dome, the leading edges of the cowl extending forwardly of the dome and adapted to extend upstream into the diffuser to receive primary air having a good velocity profile, the space between the dome and the cowl forming a plenum chamber for the equalization of primary air pressure over the entire outer surface of the dome; a mixing section connected directly to the trailing edges of the dome and the cowl, the walls of said mixing section converging over their entire length and having a plurality of openings therein; whereby secondary air on the outside of the liner is diffused between the walls of the combustion chamber and the converging cowl and mixing section 5. For use in a combustion system including a com bustion chamber having generally parallel walls and a short diifuser supplying primary and secondary air, a cowled dome liner adapted to be positioned in said chamber comprising: a dome section defining the primary combustion zone, said dome having a plurality of openings therein for the injection of primary air; a cowl surrounding said dome, said cowl having a protruding snout at its leading edge adapted to extend upstream of the dome into the diffusenan intermediate portion spaced from the dome and in close proximity to the walls of the chamber, .and a downstram portion converging towards the dome; a mixing section connecteddirectly to the trailing edges of the dome and cowl, at least the upstream portion of the mixing section converging in the same manner as the downstream portion of the cowl; whereby primary air havinga good velocity profile is received by said snout and distributed within the space between the cowl and the. dome, and secondary air is accelerated between the intermediate portion of the cowl and the chamber walls and diffused in the space between the chamber walls and the convergent portion of a cowl and mixing section.

6. For use in a combustion systemincluding a combustion chamber having generally parallel walls and a short difiuser supplying primary and secondary air, a cowled dome liner adapted to be positioned in said chamber comprising; a dome section defining the primary combustion zone, said dome having a plurality of openings therein for the injection of primary air; a cowl spaced from and surrounding said dome; said cowl having a protruding snout at its leading edge adapted to extend upstream of the dome into the difiuser, a downstream portion convergent toward the dome, and an intermediate portion in close proximity to thewalls of the chamber defining an uninterrupted passage therebetween; a mixing section connected directly to the trailing edges of the dome and the cowl, said mixing section converging over its entire length in the same manner as the downstream portion of the cowl and having a plurality of openings therein for the injection of secondary air; whereby primary air having a good velocity profile is received by said shout .and distributed within thespace between the cowl and the dome, and secondary air is accelerated in the passage between the cowl and the chamber walls and diffused in the space between the chamber walls and the converging portion of the cowl and the mixing section.

References Cited in the file of this atent 1 UNITED STATES PATENTS Great Britain Aug. 12, 1949 

